Contact lenses in wide use today fall into two general categories. First, there are the hard or rigid type lenses that are formed from materials prepared by the polymerization of acrylic esters, such as poly(methyl methacrylate) (PMMA). Secondly, there are the gel, hydrogel or soft type lenses made by polymerizing such monomers as 2-hydroxyethyl methacrylate (HEMA) or, in the case of extended wear lenses, made by polymerizing silicon-containing monomers or macromonomers. Solutions that wet lenses before insertion into the eye are required for both the hard and soft types of contact lenses, although the formulations of the solutions for hard and soft type lenses have tended to differ based on the different desired properties of the solutions. Regardless of lens type, after contact lenses are inserted in the eye, ophthalmic solutions for rewetting, lubricating, and/or enhancing wearer comfort are sometimes applied to the eye by means of a drop dispenser.
Isotonic solutions for improving the comfort of wearing soft contact lenses by being added directly to the contact lens while in the eye are known. Such solutions typically contain viscosity enhancing agents, lubricants, surfactants, buffers, preservatives, and salts. For example, Sherman discloses in U.S. Pat. No. 4,529,535 a rewetting solution that is particularly useful for rigid silicone copolymer contact lenses, including extended wear lenses. In one embodiment, the rewetting solution contains the combination of hydroxyethylcellulose, poly(vinyl alcohol) and poly(N-vinylpyrrolidone).
Ogunbiyi et al. disclose in U.S. Pat. No. 4,786,436 a wetting solution comprising collagen and other demulcents such as hydroxyethylcellulose, methylcellulose, carboxymethylcellulose, hydroxypropylmethylcellulose, hydroxypropylcellulose and the like.
Su et al. disclose in U.S. Pat. No. 4,748,189 ophthalmic solutions for improving the exchange of fluid in the area underneath the hydrogel contact lens to allow tear exchange to occur, thereby preventing the accumulation of waste matter and debris under the lens. The solution contains a hydrogel flattening agent, for example, urea, glycerin, propylene glycol, sorbitol, or an amino-ethanol. Surfactants that are useful in the solution include poloxamer and tyloxapol. Suitable lubricants include hydroxyethylcellulose, poly(vinyl alcohol) and poly(N-vinylpyrrolidone).
Winterton et al. disclose in U.S. Pat. No. 5,209,865 a conditioning solution for contact lenses that comprises a combination of a poloxamine and a poloxamer surfactant, each having an HLB (hydrophilic-lipophilic balance) of seven or below. The solution according to the invention forms a uniform hydrophilic film on a lens surface for which proteins have very little affinity. As such, a contact lens contacted by the solution is said to have a coating that provides a prophylactic effect to the lens.
Zhang et al. disclose in U.S. Pat. No. 5,604,189 and U.S. Pat. No. 5,773,396 a composition for cleaning and wetting contact lenses comprising (i) a non-amine polyethyleneoxy-containing compound having an HLB of at least about 18, (ii) a surface active agent having cleaning activity for contact lens deposits that may have an HLB less than 18, and (iii) a wetting agent. Such compositions can include, as the wetting agent, an ethoxylated glucose derivative such as glucam as also disclosed in U.S. Pat. No. 5,401,327 to Ellis et al. Tyloxapol is a conventional surface active agent, used for example in Allergan's Complete™ multipurpose solution, which agent has cleaning activity for contact-lens deposits and has an HLB less than 18.
Unlike hard lenses, the soft type of contact lenses have a tendency to absorb significantly more fluids. While it is desirable to increase contact lens wearer comfort, it is not desirable to alter lens dimensions from the manufacturer's finished product specifications through lens swelling. Some compounds useful in ophthalmic solutions to increase contact lens wearer comfort can cause lens swelling resulting in decreased visual acuity.
It would, therefore, be desirable to have an ophthalmic solution that could be applied to a contact lens that not only rewets the lens but also provides controlled release wetting of the lens over a period of time until such lens is removed from the eye and cleaned or disposed. It would also be desirable to have an opthalmic solution that preserves visual acuity by controlling lens swelling typically associated with hydrogel contact lenses treated with high concentrations of polyethers.